fix(brightness): cap panel backlight at 98%

Above ~64530/65535 the firmware brightness curve overflows and blanks the
backlight, so setting 100% went dark.

Assisted-by: AI

Author: AndrewDemsDS

quickshell/ii/services/Brightness.qml

@@ -160,7 +160,9 @@ Singleton {
                 const rawValueRounded = Math.max(Math.floor(brightnessValue * monitor.rawMaxBrightness), 1);
                 setProc.exec(["ddcutil", "-b", busNum, "setvcp", "10", rawValueRounded]);
             } else {
-                const valuePercentNumber = Math.floor(brightnessValue * 100);
+                // Cap at 98%: on panels where amdgpu applies a firmware brightness curve, raw
+                // values above ~64530/65535 overflow the curve and blank the backlight entirely.
+                const valuePercentNumber = Math.min(Math.floor(brightnessValue * 100), 98);
                 let valuePercent = `${valuePercentNumber}%`;
                 if (valuePercentNumber == 0) valuePercent = "1"; // Prevent fully black
                 setProc.exec(["brightnessctl", "--class", "backlight", "s", valuePercent, "--quiet"])